I think Iris and Violet are fine together, but are you planning on having more kids? If you are, and you get another girl, would you continue the flower theme? I would just plan ahead about that before definitely deciding on Iris.

I'm unclear whether Mae and Iris are your choices for first names or middle names?

I love Mae and Iris. They're both gorgeous, but, if I already had a daughter named Iris, I'd rule out Iris as a second daughter's name. Too matchy. So, that leaves you with Mae, which is great because Mae is lovely and matches well with Violet! I like a previous poster's suggestion of MaeVivienne. It's beautiful.